1. Field of the Invention
This invention relates to a non-contact IC card and, more particularly, to initialization of a data processing means incorporated in the IC card.
2. Description of the Related Art
FIG. 4 shows the structure of a conventional non-contact IC card which has an IC chip 5, a data transmitting antenna 6, a data receiving antenna 7, a battery 8 and an oscillator 9. A CPU 1 is formed on the IC chip 5. A ROM 2a, a RAM 2b, a data modulation circuit 3 and a data demodulation circuit 4, each of which is connected to the CPU 1, are also formed on the IC chip 5. The data transmitting antenna 6 and the data receiving antenna 7 are connected to the modulation circuit 3 and the demodulation circuit 4, respectively. The battery 8 and the oscillator 9 are connected to the CPU 1. The whole of the IC card is molded with a resin or the like to improve its resistance to environmental influences.
The CPU 1 is supplied with a power source voltage from the battery 8 and is also supplied with a clock signal from the oscillator 9. The CPU thereby operates on the basis of a program previously stored in the ROM 2a. This IC card is designed to transmit and receive data with an external device by using electromagnetic waves. At the time of data reception, an external electromagnetic wave is received by the receiving antenna 7 and is demodulated by the demodulation circuit 4 into data which is supplied to the CPU 1. The data is processed in the CPU 1 and is stored in the RAM 2b if necessary. At the time of data transmission, data is output from the CPU 1 to the modulation circuit 3 to modulate a carrier wave in this circuit, and an electromagnetic wave thereby formed is transmitted through the transmitting antenna 6.
To perform the desired operation of the CPU 1 on the basis of the program stored in the ROM 2a, it is necessary to initialize the CPU 1 formed on the chip 5 before driving the same. However, since the whole of the IC card is enclosed by the resin, the CPU 1 cannot be initialized after the resin molding. Conventionally, a reset terminal 10 connected to the CPU 1 is previously lead out from the IC chip 5. A reset signal is supplied to the CPU 1 through the reset terminal 10 to initialize the CPU 1 before resin molding. Thereafter, the whole of the IC card including the reset terminal 10 is molded.
The connection between the CPU 1 and the battery 8 is constantly maintained and the IC card therefore continues operating until the battery 8 is used up. For this reason, if an external disturbance exceeding the proof level of the IC chip 5 is applied to the IC card, there is a risk of a runaway of the CPU 1. It is possible that temperature, electromagnetic waves, light, radioactive rays, mechanical stress, static electricity and the like act as external disturbances. However, if a runaway of the CPU 1 takes place, there is no means to stop it since the CPU 1 cannot be initialized after the IC card has been resin molded, resulting in a disabled state of the IC card.